The safe propagation of the human race is fundamental to the well being of our society. One need not be a parent to realize the importance of improved medical devices and methods in delivering a fetus safely into this world. Currently, there are two major methods for delivering a fetus, the Cesarean section delivery and the vaginal delivery.
In Cesarean section deliveries, the fetus is delivered through an incision made in the uterus and a corresponding incision made in the abdomen. An upward pulling force is required in order to pull the fetus through the incisions and out of the mother. Often the force is provided by the doctor's hands directly pulling the fetus through the abdominal incision.
In vaginal deliveries, the fetus is delivered through the vaginal passage after the cervix has fully dilated and effaced. Passing the fetus through the vaginal passage requires that the vaginal muscles be forced to stretch because the fetal head is much larger than the vaginal passage under normal circumstances.
Some stretching force is applied to the vaginal tissues by the mother herself. The involuntary contractions of the uterus during labor push the fetus (typically the fetal head) into the vaginal passage to stretch the vaginal tissues. The stretching force of these involuntary uterine contractions is combined with the stretching force caused by voluntary contractions of the mother's abdominal muscles as the mother tries to push the fetus out of the uterus.
Often the forces described above are not strong enough or are not medically advisable to use in extracting the fetus. Supplementary force may be applied with a fetal vacuum extractor, for example, in conditions of dystocia (i.e., slow or difficult labor or delivery), uterine inertia, maternal exhaustion, maternal distress, or fetal distress.
In a conventional fetal vacuum extractor, a vacuum cup is sealed over a portion of the fetal head (e.g., the occiput). A flexible tube connects the vacuum cup to a vacuum pump operated by a secondary operator such as a nurse. The vacuum pump allows the nurse to provide a vacuum within the vacuum cup thereby creating suction between the fetal head and the vacuum cup. As long as a sufficient vacuum is maintained, the primary operator, such as a doctor, may pull on the vacuum cup handle thereby applying traction (i.e., a pulling, delivering force) to the fetal head.
Bodily fluids on the fetal head assist in making a seal between the fetal head and the vacuum cup to define a chamber. However, the vacuum is often unintentionally released as fluid seeps against the normal flow of a one-way valve provided in the vacuum pump. Vacuum is also unintentionally released when the seal between the fetal head and vacuum cup is broken. In order to minimize the chances of fetal injury, the vacuum is intentionally lowered between contractions or when the vacuum is determined to be too strong. Therefore, the vacuum must be constantly monitored and adjusted, and must have a method to release or lower the vacuum.
The conventional fetal vacuum extractor is designed so that the doctor pulls on the handle to provide traction while the nurse monitors and adjusts the vacuum. The doctor instructs the nurse to provide more (or less) vacuum when the doctor determines that the vacuum is too weak (or too strong).
Unfortunately, time elapses between the time the doctor determines that a vacuum is needed and the time a vacuum is provided. This time includes the time required for a doctor to issue oral instructions after the doctor has determined that a vacuum adjustment is needed, and the time required for a nurse to respond to the oral instructions. Typically, this time is only a matter of seconds. However, because the vacuum may be lost very quickly, this additional response time may cause disengagement of the vacuum cup with the fetal head, interrupting the delivery. If the vacuum is too strong, this additional response time may cause injury to the fetal head.
The conventional fetal vacuum extractor also has a relatively large volume of fluid that is sealed off during the vacuuming operation. Therefore, more fluid must be pumped out of the sealed volume in order to maintain a given vacuum compared to a system in which the sealed off fluid volume is less.
Therefore, what is desired is a fetal vacuum extractor in which a single operator, such as a doctor, can conveniently and directly control the vacuum within the vacuum cup at the same time as pulling or applying force to the vacuum cup. Furthermore, a fetal vacuum extractor having a relatively low sealed off fluid volume is desired because the vacuum can be created faster with fewer pumps and with a smaller, more compact pump.